1. Field of the Invention
The present invention relates to an electrophotographic device, and particularly to an electrophotographic apparatus using a longitudinally continuous printing paper.
2. Description of the Related Art
Japanese Patent Publication Laid-Open No. Hei 4-321062 discloses the art of an arrangement wherein a printing paper reversing device is provided between two electrophotographic apparatus disposed adjacent to one another and using one electrophotographic apparatus located upstream of the paper reversing device where a toner image is fixed on one side of a printing paper, and upon turning upside down by the printing paper reversing device the printing paper fed out from the electrophotographic apparatus, the printing paper is fed into another electrophotographic apparatus, downstream of the paper reversing device, where a toner image is fixed on another side of the paper, whereby respective toner images will be obtainable on both sides of the paper.
In an electrophotographic apparatus system constituted with some electrophotographic apparatus operatively linked together to provide the respective toner images on both sides of a printing paper, setting a preheater of a downstream-side electrophotographic apparatus at a temperature higher than the glass transition point of toner will entail such trouble that the toner image formed by the foremost electrophotographic apparatus undergoes re-softening and the toner image thus re-softened goes through friction with the preheater, staining said preheater and suffering degradation as well.
Therefore, where printing is effected on both sides of a printing paper in such an above-mentioned configuration of the electrophotographic apparatus system, it was required that the process of fixing be implemented with the minimum thermal efficiency which would not ill-affect the toner image formed by the foremost electrophotographic apparatus, whereby there used to be inevitably no alternative but to set the printing speeds of the respective electrophotographic apparatus to lower values.
However, selecting the printing speeds of electrophotographic apparatus to such a low speed suited to the electrophotographic apparatus system results in failure of those electrophotographic apparatus to fully demonstrate the originally feasible printing speeds in case where printing is effected with each of these electrophotographic apparatus put into separate run independently of one another, coming to a finding that the discrepancy of run between the respective cases, one where printing is carried out with the electrophotographic apparatus applied as the electrophotographic apparatus system, and the other where the individual electrophotographic apparatus are brought into run separately, still remains uncorrected.
In the description hereunder, the configuration of printing with the electrophotographic apparatus applied as the system is referred also to "tandem printing". Further, the formation of printing wherein individual electrophotographic apparatus are driven into separate run independently of one another is otherwise called as "single printing".